Diff Identification

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paul 300358
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Re: Diff Identification

Postby paul 300358 » Wed Mar 06, 2019 8:40 pm

The BTA carrier is the later carrier and is stronger than the ATA carrier.

philthehill
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Re: Diff Identification

Postby philthehill » Wed Mar 06, 2019 8:40 pm

The BTA is the identifier for the later carrier which has a stronger web in the area marked with an asterixis in the diagram below.
img360.jpg
img360.jpg (1.55 MiB) Viewed 565 times
The parts are not interchangeable so you cannot put BTA diff parts into an ATA carrier and vice versa.


paul 300358
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Re: Diff Identification

Postby paul 300358 » Thu Mar 07, 2019 2:00 pm

Going off phil's chart, your carrier will be a BTA as it already has a 3.9:1 crown wheel & pinion fitted.

RobThomas
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Re: Diff Identification

Postby RobThomas » Thu Mar 07, 2019 3:00 pm

The second one on the chart is also a 3.9 but with an ATA casing so it could be either version. I believe (but may be wrong) that the W1500/Riley 1.5 had ATA assemblies but the Midget had BTA ones.
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paul 300358
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Re: Diff Identification

Postby paul 300358 » Thu Mar 07, 2019 3:14 pm

Just testing Rob. It should be easy for Alawrence to find out though as he has the diff off the car. Will either diff fit the axle providing the complete assembly is obtained?

RobThomas
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Re: Diff Identification

Postby RobThomas » Thu Mar 07, 2019 5:19 pm

Both will fit. I doubt that an average 1275 will have enough guts to easily break an ATA version, but you never know. :D
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philthehill
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Re: Diff Identification

Postby philthehill » Thu Mar 07, 2019 7:26 pm

Rob
You may be right.
The only problem I have ever had with an ATA carrier unit at 140bhp is the sun and planet gears breaking up.

I would love to put an BTA carrier and a 4.8 diff ratio together but they are not compatible so the ATA carrier with 4.8 it has to be.

The 4.8 is from the A35 van.

Phil


alawrence10360
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Re: Diff Identification

Postby alawrence10360 » Sat Mar 09, 2019 8:38 am

I have found a dealer who has 3 diffs all 3.9:1 out of the axles
Apart from physical damage to teeth what should I look for ?

alawrence10360
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Re: Diff Identification

Postby alawrence10360 » Sun Mar 10, 2019 7:38 am

anything ??

philthehill
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Re: Diff Identification

Postby philthehill » Sun Mar 10, 2019 8:13 am

Make sure that it turns without any difficulty above and beyond the pinion preload; and without any roughness to the feel when turning,


alawrence10360
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Re: Diff Identification

Postby alawrence10360 » Sat Mar 16, 2019 6:48 pm

So,fitted the replacement diff and seems ok, no noises ,however it has a slight leak from the pinion seal.
Whats the easiest way to solve this given that I buggered up the last one by over tightening the nut when I followed the instructions in the manual and this video
If you watch from 24 mins you will see he also tightened to 140ftlbs. I did the same thing albeit out of the car.
https://youtu.be/n7Uqn0zeFuU

philthehill
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Re: Diff Identification

Postby philthehill » Sat Mar 16, 2019 9:00 pm

When tightening the pinion nut constant checks should be made to ensure that the pinion preload does not exceed 13lb. in.

Personally I would set the pre-load as required and make a note of the torque setting required to get there and hopefully the torque and pre-load will be one and the same at the same time.

In some ways it is as important to get the pre-load correct than get the torque right.

The procedure for setting the pinion pre-load is set out in BMC Wksp Manual Section HH. Section 2 Adjusting Pinion Bearing Preload; and it does state that the pre-load should be checked during the tightening process of the pinion nut.


alawrence10360
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Re: Diff Identification

Postby alawrence10360 » Sat Mar 16, 2019 9:20 pm

Thanks Phil
So that video is Bo@*#@ks !
Can this be done in the axle ?

philthehill
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Re: Diff Identification

Postby philthehill » Sun Mar 17, 2019 8:37 am

Having the compressible spacer brings its own problems as you are finding out.

The old style non compression spacer which had to be built up was much better in that once the pre-load was determined the pinion nut could be undone and tightened numerous times without any concerns as to the preload.

The compression spacer made the setting of the pinion preload in the factory much easier and quicker so saving money.

The pinion preload check should not be done in the axle unless the half-shafts are removed as the drag of the half-shafts etc. has a direct bearing on the pre-load reading. Ideally the pinion pre-load should be set before the crown wheel is fitted but for the purposes of fitting a new pinion seal the turning resistance of the crown wheel and pinion as a whole can be totaled up.

I make no comment as regards the video other than having watched the video I do not remember hearing any comment regarding the pinion preload.

Phil


oliver90owner
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Re: Diff Identification

Postby oliver90owner » Sun Mar 17, 2019 9:51 am

IIRC, back in the 70s Ford diffs were built up using a collapsible spacer to clearance/backlash specification. The collapsible spacer was measured and replaced by the permanent solid variety. I may be wrong on that, as it is a distant recollection from a service manual of the day.

alawrence10360
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Re: Diff Identification

Postby alawrence10360 » Sun Mar 17, 2019 10:34 am

I think I will give it a go
I know somone mentioned marking the nut and tightening it back up to that point. Whats the thoughts on that ? I dont believe I have 13ftlbs drag at the moment as it spun quite easily on the bench but I thought I would leave well alone

philthehill
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Re: Diff Identification

Postby philthehill » Sun Mar 17, 2019 1:58 pm

Marking the nut, the flange and the end of the pinion is a good idea and that is what I would do without access to the specialist tools.

Fit the flange and pinion marks aligned so as to keep everything as it was.

Progressively torque the pinion nut until the flange and nut marks are aligned. When the marks are aligned compare the resistance you felt before removing the nut/flange and after re-fitting.

The measurement is 'lb inch' not 'lb ft' - there is quite a difference between the two.

Metric wise .........…. 0.126 to 0.149 kg.m which is next to nothing.

With the marks all aligned and with the pinion turning post seal replacement with no tightness or roughness you will be alright.

Phil


alawrence10360
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Re: Diff Identification

Postby alawrence10360 » Sun Mar 17, 2019 2:17 pm

Super

Declan_Burns
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Re: Diff Identification

Postby Declan_Burns » Sun Mar 17, 2019 6:28 pm

oliver90owner wrote:
Sun Mar 17, 2019 9:51 am
IIRC, back in the 70s Ford diffs were built up using a collapsible spacer to clearance/backlash specification. The collapsible spacer was measured and replaced by the permanent solid variety. I may be wrong on that, as it is a distant recollection from a service manual of the day.
Not a bad idea at all. I have about 10 blanks already made to do exactly that.
Regards
Declan


Regards
Declan

alawrence10360
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Re: Diff Identification

Postby alawrence10360 » Fri Mar 22, 2019 8:32 pm

philthehill wrote:
Sun Mar 17, 2019 1:58 pm
Marking the nut, the flange and the end of the pinion is a good idea and that is what I would do without access to the specialist tools.

Fit the flange and pinion marks aligned so as to keep everything as it was.

Progressively torque the pinion nut until the flange and nut marks are aligned. When the marks are aligned compare the resistance you felt before removing the nut/flange and after re-fitting.

The measurement is 'lb inch' not 'lb ft' - there is quite a difference between the two.

Metric wise .........…. 0.126 to 0.149 kg.m which is next to nothing.

With the marks all aligned and with the pinion turning post seal replacement with no tightness or roughness you will be alright.

Phil
job done
no noise
no leaks


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